I know a lot of people here dont really like the way the low fare airlines operate but I was just wondering how they do it , how can the likes of Ryanair and Easyjet offer such low fares and still post such big profits ??

They fly one aircraft type
Fly their crews for multiple sectors and long days in Jack-of-all-trades fashion
Fly to small out of the way airports where charges are low or even actually get paid to fly there
Fly ticketless on line with real-time charges and give you no rights whatsoever in case of delay/cancellation.
Have no onboard service but sell stuff at high prices.
Target a market that will otherwise not travel at all.

These are just some ideas. There is a good book called simply "No Frills" which exposes these airlines for what they are.

high loadfactors.
Where the regulars often have 20-30% empty seats, having 10% empty seats is rare on a lowcost.
If there are more empty seats they just cancel the flight for 'technical problems' and reschedule the passengers without refund or anything (as per the terms of the sale).

low operating cost.
Less flight attendants per aircraft. Most large airlines have more than the legal minimum, lowcosts do not.
No food or free drinks on board. Thus lower cost of service and you need less fuel (because lower weight).
Often lower luggage allowance. Again this lowers the fuelbill.

More seats per aircraft.
Coupled with less luggage per seat, this means you can carry more passengers on the same flight using the same fuel.

(often) lower salaries for the staff.

fleet commonality.
Need less different spares in stock, and less differently trained maintenance and flightcrew.
If you fly 10 types you need more spare crews with the same number of aircraft because most won't be current on all those types.
It also helps if you can buy big (Southwest will get a lower unit price on 737s when buying 100 than say KLM when buying 20. This is of course just a random example).

Fly into smaller airports.
Some lowcosts fly into small airports (more or less) close to the cities instead of the major airports.
Landing and parking/handling fees here are lower.

- They sell tickets only by internet or telephone to dump charges of staff.
- Prices rise with the loadfactor. The cheapest price is only on 30% of the seats (an advance for people who book early enough).

-US don't pack them in as tightly as possible
-They don't sell food, but offer small snacks for free like the major US airlines(no meals though).
-fly to large and small airports(LGA, PHL, LAX, SEA, or smaller ones like OAK and SJC instead of SFO).
-Delay/Cancellation may be a little more stingy compared to the major airlines(depending on the LCC), but laxer restrictions are also more common(FL charges $50 to change flight, B6 $25, and WN only fare difference compared to $100 at most majors).

In Europe, they fly pretty short legs, and the ground time is very short.
By this way, they can make one or two extra rotation per day.
Since they have no catering (the only trolley with some sandwiches and the drinks is changed only every 2 or 3 rotations), it is easy to reduce the ground time.
To save additional time and money, the cabin is cleaned by the crew.